    [Patent document 1] JP-2003-166868 A
Patent document 1 discloses a an in-vehicle apparatus that displays a present room temperature, a present fuel mileage, a room temperature after change, and a fuel mileage estimate after room temperature change. In this apparatus, after calculating fuel consumption amounts of the air-conditioning apparatus according to a present room temperature and a room temperature after change, respectively, the calculated fuel consumption amounts are reflected on a fuel consumption estimate value.
In the above technology, the room temperature prior to the change only uses a present room temperature. Thus, there is a possibility that the vehicle was not driven by a user under the same temperature as the present room temperature. If the vehicle was not driven in the past under the present room temperature, the user naturally has no experience of driving the vehicle under that present room temperature. That is, the fuel consumption under a temperature that the user has not experienced is used for display as a comparison target for the fuel consumption under the temperature after change. Such a display may result in only providing the user with an unrealistic feeling.